bunpen: exec: log more verbosely

pkgs/by-name/bunpen/rt/ext/exec.ha

@@ -2,6 +2,7 @@
 
 use errors;
 use errors::ext;
+use fmt;
 use log;
 use os;
 use os::exec;
@@ -13,6 +14,16 @@ use types::c;
 export fn execve(path: str, argv: []str, envp: []str = []) rt::errno = {
   let path_buf: [path::MAX]c::char = [0...];
 
+  {
+    let logv: []fmt::formattable = [];
+    defer free(logv);
+    append(logv, "[exec] execve:");
+    append(logv, path);
+    for (let arg .. argv)
+      append(logv, arg);
+    log::println(logv...);
+  };
+
   syscall(
     rt::SYS_execve,
     make_cstr(&path_buf, path): uintptr: u64,